The present invention relates to the fields of radiology and nuclear medicine, and in particular to the use of rectilinear scanners for the performing of a number of diagnostic studies of bodily tissue and organs.
The fields of radiology and nuclear medicine have long been concerned with the development of techniques for the non-invasive diagnosis of medical conditions of human or animal tissue. Generally procedures involve the use of x-ray radiation that is passed through a body to provide static or dynamic transmission studies, or alternatively, the use of radiopharmaceuticals that are introduced into the patient such that their distribution or concentration can be viewed by the detection of the resulting gamma ray emissions of variable intensity.
Initially these systems used an analog rectilinear scanner to generate static images wherein a scintillation-type gamma ray detector equipped with a focusing collimator was moved continuously, through a series of parallel sweeps, to scan the region under study.
Rectilinear scanners have more recently been used with a dual energy radioactive source for conducting transmission bone densitometry studies. Early analog devices have been used for conducting emission studies with an injected isotope as referenced above. In either case rectilinear scanners have seen very limited use due to the development of so-called xe2x80x9cgamma cameraxe2x80x9d systems developed in the last decade.
Because of the interest in performing dynamic studies such as myocardial perfusion, wall motion, lung perfusion and lung ventilation, systems were developed to view the entire region of interest. These xe2x80x9cgamma cameraxe2x80x9d systems utilized a large diameter sodium iodide crystal in conjunction with a matrix of photomultiplier tubes and a multi-channel collimator to perform a large variety of emission studies. The problem with gamma cameras using scintillation detector crystals is that the resolution is limited by both the light coupler between the detector and the photomultiplier and, more importantly, by the scattering of the radiation emitted from the in vivo region of investigation. Even if the resolution of gamma cameras were adequate they do not produce an image of the tissue of actual size. Gamma camera systems are also extremely expensive, require a large space to be used, and necessitate a relatively high level of operator training. In addition, the use of gamma cameras for performing static studies has tended to lower their cost effectiveness due to there use on these low revenue static studies.
As a result of these factors, there is a need for a relatively inexpensive, portable and easy to use rectilinear scanner that can be used for diagnostic applications requiring the generation of static images. This will operate to free the gamma camera systems for performing the high revenue dynamic studies for which they are intended.
The present invention relates to the use of rectilinear scanners for performing emission and transmission studies to provide diagnostic non-invasive measurements of body tissue.
The apparatus utilizes a housing that can be easily adapted for the use of different radiation sources to conduct these diagnostic studies. For example, both a dual energy radioactive source, such as gadolinium-153, or an x-ray generator can be placed in the housing of the scanner assembly. The radioactive source can be used for conducting transmission studies, and the x-ray source can be used for conducting both transmission and fluorescence studies. The x-ray source, in analogy with the dual photon energy source commonly used in bone densitometry, can use two energy levels to provide an x-ray bone densitometer. Alternatively, the detector, collimator and software package can be replaced to permit the performing of emission scintigraphy studies. A number of interchangeable collimators are used having different focal lengths, and sensitivity and which are designed to operate for emitting isotopes with different energy levels. The wall thickness of the collimator columns is altered to compensate for differing energy levels.
As described in U.S. patent application Ser. No. 050,726 filed on May 15, 1987, a rectilinear scanner can be mounted on an assembly which permits the radiation source and detector to be rotated about a patient so that scanning can be conducted at any angle without having to move the patient. This permitted improved bone densitometry studies of patients suffering from bone degeneration. The present application discloses the use of this multidirectional capability for a number of other diagnostic studies for which digital rectilinear scanners have not been used.
These studies are used to generate images of specific bodily tissue and organs as well as provide quantitative information regarding the volume of organs, tissue density, bone turnover rate, and organ studies such as thyroid uptake. Each study performed by the scanner is controlled by a software package designed for that study.
The present invention also incorporates the use of a laser, or other light source or some mechanical means for identifying a specific portion of tissue being scanned. The user can record a position of particular interest relative to the scan being conducted using the laser. The software can then analyze detected characteristics of the tissue for the identified region of interest.
The scanner assembly also incorporates sensors that detect any obstruction to the movement of the detector during scanning, or during rotation of the scanner assembly. These sensors either deactivate the motor drive thereby stopping any further motion, or they actuate an alarm to inform the operator of some obstruction. This reduces the risk of injury to the patient or damage to the system during operation.
A separate table is used to support the patient so that any region of the body can be positioned within the scanning area of the device. One embodiment utilizes a detector that is rotatable to permit emission studies to be performed on a person in a sitting or supine position.
Emission studies utilize a zoom capability of the detector to obtain images of different focal planes within the tissue being imaged.
The above and other features of the invention including various novel details of construction and combinations of parts will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular multidiagnostic rectilinear scanner systems embodying the invention are shown by way of illustration only and not as a limitation of the invention. The principles and features of this invention may be employed in varied and numerous embodiments without departing from the scope of the invention.